Fuel injection systems may include a plurality of cylinders, in each of which a fuel-air mixture is introduced and then ignited. The cylinders may include inlet and outlet valves driven with cams on an inlet valve camshaft or an outlet valve camshaft. The opening and closing times may be set by a control unit in dependence on the camshaft position signal provided by a camshaft sensor.
To determine the mass of air required in each case for the fuel-air mixture, it is typical to use the camshaft position signal provided by the camshaft sensor as an actual position signal for each of the cylinders of the fuel injection system. Furthermore, a setpoint phase shift of the inlet valve camshaft may be calculated on the basis of the setpoint air mass and the engine speed. The phase shift may then be controlled using the camshaft position signal and the setpoint phase shift.
A method for controlling the quantity of air and/or the fuel-air ratio for individual cylinders of an internal combustion engine is taught in DE 10 2005 057 974 A1. In that document, the amplitude and frequency of a signal, which is not cylinder-specific and is influenced by an actuator which is not cylinder-specific, is determined and is used to identify cylinder-specific signal components, and the cylinder-specific signal components are used as the basis for actuating the actuator, which is not cylinder-specific.
Furthermore, some systems drive the high-pressure pump of a fuel injection system using the cams of a camshaft. In such a fuel injection system, if the pressure in the rail and/or the delivery volume of the high-pressure pump increases, then the torque to be provided therefor by the camshaft also increases. This increased increases torsion of the camshaft. In turn, this leads to undesired deviation in the control times of the inlet valves, which is greater the greater the distance of the respective cam from the camshaft sensor. The undesired deviation in the control times in turn affects the quantity of air with which the respective cylinder is filled, and thus also the associated quantity of fuel.